Bern, Burgerbibliothek, Cod. 402

Why the shape of the flame is pyramidal.

the air

The shape is pyramidal, and Democritus says that it is because the parts themselves are cooled as they reach the extremities, gathering into a small point and finally ending. Certain others of the ancients say it is due to the movement of the air striking it. For there is always a vapor above the flame, and in the movement of the plane, the air cools it, and because of the movement of the striking wind, the fire is forced to stand still and form in this way. But he referring to Aristotle's view says neither of these two [is correct], and that it ends more because of movement than because of cooling; the movement of the striking air is entirely ridiculous to them. For the fire is moved by itself, and it moves the air more than it is moved by it, by pushing it away, since even when there is force, the sharpness of the flame is no less. Furthermore, the stripping away as if parts are being shed is absurd; he treats it as if it were something light and superficial occurring equally from all sides, and even more so when there is a greater wind. But in fact, in still air, the flame reaches its peak point most clearly, since it is not hindered by wind from obstructing its upward motion and bending it or throwing it about. This [view], then, is not true, nor even very intelligent. But if fire is in motion and flow, and the reaching of flowing things is always toward something smaller—since there is no influx from above, and it is necessary that the lower place be maintained and that the continuous [flow] be preserved—it must become more constricted, so this would be the cause of the flame’s shaping. For the source from below is most powerful and wide. After this, it is always smaller and ends in motion